A new stretch of toll road through central Texas linking Austin to San Antonio, State Highway 130, may soon have the highest posted speed limit in the hemisphere. Once completed, sections five and six of the project, totaling 41 miles, may be the first to allow drivers to travel 85 miles per hour—ten mph faster than Interstate 35, which the project parallels. I-35 in the Austin area, however, rarely flows at full speed; its south- and north-bound lanes rank as the 14th and 16th, respectively, most congested highways in the nation. Promoters of the new toll road hope the faster speed will help to lure drivers off of I-35 and onto SH 130. Sections one through four of the project are currently in operation, and drivers are limited to 80 mph, the previous maximum allowable speed on highways in the state. However, last year the state legislature passed a law raising the allowable limit to 85 mph on all highways deemed safe enough for the speed.

The exact toll structure has not yet been defined, but the base rate for passenger vehicles could be as high as 12.5 cents per mile, a total of $5 for the 41-mile stretch. As Nate Berg noted in Atlantic Cities, in free flowing traffic, the additional speed would save drivers just shy of four minutes on a trip from San Antonio to Austin.

While many drivers in the state are enthusiastic about the prospect of shortened driving times over the congested I-35, auto insurance companies and highway safety advocates are less excited. Quoted in the Austin American Statesman, Jerry Johns, a spokesman for the Southwestern Insurance Information Service, noted that the increased speeds would likely result in higher death and injury rates and called the idea of 85 mph speed limits on public highways “simply ludicrous.” The Texas Department of Transportation has not yet done the required analysis to determine whether the road could accommodate the 85 mph limit, but says it is comfortable with the idea of increased speed limits. As Darren McDaniel, the DOT’s speed management director, noted in a conversation with WOAI News Radio, “The more people we can get to travel a uniform speed, the safer are the conditions that will exist.” What actions, if any, the DOT will undertake to limit the variation in speed between drivers remain to be seen.

Whatever the safety and congestion relief impacts of SH 130, an 85 mph limit would certainly have negative impacts on fuel economy. Based on US Department of Energy estimates that each additional five mph in excess of 60 mph results in five percent poorer fuel economy, the average driver could expect to see a 25 percent reduction in fuel economy when traveling 85 mph versus 60 mph.